Background: This study investigated the association between obesity and cardiometabolic disease clusters in Korean adults aged 19-39 years. Methods: We included 3,785 participants (1,767 men and 2,018 women) aged 19-39 years who participated in the Korea National Health and Nutrition Examination Survey (2020-2022). The risk factors for cardiometabolic disease were defined as follows: high blood pressure; hypertriglyceridemia; hyperuricemia; and high low-density lipoprotein cholesterol, low high-density lipoprotein cholesterol, high fasting plasma glucose, elevated alanine aminotransferase levels. Results: The prevalence of participants with ≥ 1, ≥ 2, and ≥ 3 cardiometabolic disease risk factors was 95.2%, 84.2%, and 65.6% in men and 90.0%, 70.5%, and 43.0%, in women with class 2-3 obesity, respectively. Compared to those for young adults with underweight/normal weight, the odds ratios (ORs) and 95% confidence intervals (CIs) for the clustering of cardiometabolic risk factors were 17.26 (8.32-35.80) for ≥ 1; 19.43 (12.18-31.00) for ≥ 2; and 22.93 (14.15-37.15) for ≥ 3 factors in men with class 2-3 obesity and 14.67 (8.00-26.91) for ≥ 1; 20.88 (12.15-35.88) for ≥ 2; and 36.26 (20.20-65.09) for ≥ 3 factors in women with class 2-3 obesity. Conclusion: Although the patients were young, the prevalence and ORs for cardiometabolic disease risk factor clusters in young adults with obesity were prominently high. Prevention and management of obesity in young Korean adults are urgently needed at both individual and public levels.

The prevalence of obesity has been increasing worldwide. Several dietary treatments have been suggested to control weight, and recent guidelines recommend individualizing the composition of macronutrients. Carbohydrates are the most important nutrients in meals, and carbohydrate restriction is a dietary strategy that promotes weight loss. A low-carbohydrate diet is effective for short-term weight loss and can help improve glycated hemoglobin, systolic blood pressure, diastolic blood pressure, and triglyceride levels; however, the long-term effects and safety of this diet remains doubtful. In the short term, there is a risk of gastrointestinal symptoms such as vomiting, diarrhea, constipation, and gastroesophageal reflux, and type 1 diabetes patients are at risk of severe hypoglycemia, while in the long term, it can lead to malnutrition and decreased exercise capacity. Thus, rather than limiting the intake of carbohydrates, it is important to limit the intake of refined grains, sugar, honey, syrup, and sweetened beverages while maintaining the planned carbohydrate intake rate and improving meal quality.

Ultra-processed foods, falling under group 4 of the Nova classification system, are manufactured from processed food ingredients such as oils, fats, sugars, starch, and protein isolates, containing minimal to no whole food. They commonly incorporate flavorings, colorings, emulsifiers, and various cosmetic additives to enhance their palatability. Ultra-processed foods have become increasingly prevalent in contemporary society owing to their convenience, affordability, extended shelf life, and enhanced taste and aroma through additives. This surge in the consumption of ultra-processed foods has sparked discussions regarding its adverse health effects. Numerous studies have highlighted that an increased intake of ultra-processed foods elevates the risk of metabolic disorders, such as cardiovascular diseases, obesity, and diabetes, along with an increased risk of various cancers. Moreover, its association with an increased mortality risk underscores the importance of recognizing that opting for these foods based solely on taste and convenience is risky. Thus, by recognizing dietary habits as modifiable factors that can prevent health issues, maintaining a balanced diet with diverse nutrient intakes is crucial for overall health. Therefore, raising awareness and understanding of ultra-processed food consumption can significantly contribute to promoting healthy lifestyles.

The prevalence of obesity in children and adolescents is increasing worldwide. Obesity in children and adolescents not only increases the risk of transitioning to obesity in adulthood but also increases the risk of cardiometabolic diseases such as high blood glucose, high blood pressure, dyslipidemia, fatty liver, and hyperinsulinemia during childhood. The goal of treating obesity in children and adolescents is not to focus on weight loss but to help children reach a healthy weight while maintaining normal growth appropriate for their age and sex. To achieve this goal, regular physical activity and exercise, dietary modification, improvement of obesity-prone environmental factors, and behavioral changes are required for a healthy lifestyle. If appropriate weight control is not achieved through lifestyle modifications, pharmacotherapy may be considered for adolescents with severe obesity aged 12 and above. Recent clinical trials have reported the efficacy and safety of pharmacotherapy in severely obese adolescents. Currently, two medications can be prescribed in Korea for patients with obesity aged 12 and above: Orlistat and Liraglutide. However, despite effective weight control through drug treatment, body weight may increase again after treatment discontinuation. Therefore, it is crucial to evaluate adherence to health behaviors during visits and continue to educate on lifestyle modifications, even during pharmacotherapy, to minimize weight regain.

Serotonin, a biogenic amine widely found in many organisms, functions as both a neurotransmitter and hormone. Although serotonin is involved in various physiological processes, this study aimed to review its role in energy metabolism. Given that serotonin cannot cross the blood-brain barrier and is synthesized by two different isoforms of tryptophan hydroxylase in the central nervous system (CNS) and peripheral tissues, it is reasonable to assume that serotonin in the CNS and peripheral tissues functions independently. Recent studies have demonstrated how serotonin influences energy metabolism in metabolic target organs such as the intestines, liver, pancreas, and adipose tissue. In summary, serotonin in the CNS induces satiety and appetite suppression, stimulates thermogenesis, and reduces body weight. Conversely, serotonin in the periphery increases intestinal motility, stimulates gluconeogenesis in the liver, suppresses glucose uptake by hepatocytes, promotes fat uptake by liver cells, stimulates insulin secretion while suppressing glucagon secretion in the pancreatic islets, promotes lipogenesis in white adipose tissue, inhibits lipolysis and browning of white adipose tissue, and suppresses thermogenesis in brown adipose tissue, thereby storing energy and increasing body weight. However, considering that most experimental results were obtained using mice and conducted under specific nutritional conditions, such as high-fat diets, whether serotonin acts in the same way in humans, whether it will act similarly in individuals with normal versus obese weights, and whether its effects vary depending on the type of food consumed, remain unknown.

Idiopathic intracranial hypertension (IIH) is characterized by increased intracranial pressure without detectable causes. Its main symptoms include headache, vision problems, and pulsatile tinnitus. Obesity is a major risk factor for IIH; therefore, weight reduction is required to ameliorate these symptoms in patients with obesity and IIH. We present four cases of obesity-related IIH whose symptoms improved through weight reduction. In three patients, the dose of IIH medications, such as acetazolamide, decreased. Based on these cases, we report that weight reduction contributes to the improvement of symptoms in patients with IIH as the main part of treatment. Further clinical research is necessary to evaluate the effects of weight reduction on IIH treatment in Korean patients.